Apparatus and method for managing dormant state in a wireless packet data system

ABSTRACT

A wireless packet data system efficiently manages a location of a packet call in a radio environment. A mobile station transmits a location registration message to a target BSC when moving to the target BSC adjacent to a source BSC. Upon receipt of the location registration message, the target BSC transmits a location update message for updating a location of the mobile station to a centralized database. Upon receipt of the location update message, the centralized database updates dormant state information for the mobile station to connect the target BSC to the source BSC. The centralized database transmits a location update result message indicating complete update of the dormant state information to the target BSC.

PRIORITY

This application claims priority to an application entitled “Apparatusand Method for Managing Dormant State in a Wireless Packet Data System”filed in the Korean Industrial Property Office on Aug. 19, 2000 andassigned Serial No. 2000-48180, the contents of which are herebyincorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a wireless packet datasystem, and in particular, to an apparatus and method for managing alocation of a packet call in a radio environment.

2. Description of the Related Art

In general, a wireless packet data system is included in a mobilecommunication system, and refers to a system for transmitting data inthe form of a packet through a wireless network. For example, the systemincludes a CDMA (Code Division Multiple Access) system, a PCS (PersonalCommunications Services) system and a future mobile communication systemsuch as a CDMA-2000 system and a W-CDMA system, standardizations ofwhich are under way.

Meanwhile, the wireless packet data system manages informationpertaining to a mobile in service in order to provide a packet callservice. Here, since the “mobile” refers to a mobile station (MS) not abase station (BS), the information on the mobile must necessarilyinclude location information of the mobile. Further, a base stationcontroller (BSC) constituting the wireless packet data system processespacket data incoming to and outgoing from the mobile according to themanaged location information of the mobile.

The location information is managed in different ways according tostates of the mobile. In an active state and a control hold state wherecertain channels are established, the location information is managedthrough a handover. That is, since the mobile performs a handover usinga dedicated signaling channel (dsch), a dedicated traffic channel (dtch)and a dedicated MAC (Medium Access Control) channel (dmch), it makes thetransition from one state to another state while maintaining one or morechannels to the BSC during a handover. Accordingly, the movement of themobile in the above states can be continuously traced by the BSC.

However, if the mobile enters a dormant state where transmission andreception of the traffic is not performed because no packet data istransmitted for a predetermined time, there exists no connection betweenthe mobile and the BSC, making it impossible to manage the location inthe same way as done in the active state and the control hold state.

The dormant state means a state where such traffic as voice and packetdata is not generated in a state where a radio channel is established.When the dormant state occurs, the wireless packet data system manages alocation of the packet call in the dormant state to prepare for laterresumption of the traffic. For this reason, the conventional wirelesspacket data system proposes the following four plans of managing apacket call in the dormant state, and adopts one of them.

In a first proposed plan, a home location register (HLR) and a visitorlocation register (VLR) take exclusive charge of the location managementof a call, and a base station system (BSS) deletes all information on acall that entered the dormant state. In this case, when a packet call inthe dormant state requests transmission of the packet data, the sameprocess as a normal new call setup process is performed. That is, aninitial call setup process, a registration process and an authenticationprocess are all performed. As a result, an exchange of radio messagesdue to the call setup process increases a load on an RF (RadioFrequency) stage, and brings about processing loads on the VLR/HLR/AC(Authentication Center) due to the registration and authenticationprocesses. In addition, performing the complicated call setup processcauses an increase in a packet buffering time, thus increasing a delaytime. In particular, it is difficult to trace a location of the mobileexisting in the dormant state, so that a paging load may increase whenthere is a request for an incoming call to the mobile from the network.

A second proposed plan is to compensate the first proposed plan. Thisplan provides a plurality of the VLRs/HLRs in order to decrease theprocessing loads of the single VLR/HLR performing the locationmanagement. In this plan, location management of the mobiles is notprocessed in the single VLR/HLR, but the mobility of all the mobiles isprocessed by a plurality of the VLRs/HLRs on a load shared basis.Therefore, the BSCs determine the VLR/HLR managing the locationinformation of the corresponding mobile using an identifier (ID) of themobile, and then acquire the mobile information through thecorresponding VLR/HLR. However, as the second plan is fundamentallyperformed in the same procedure as the first plan, the second plan issomewhat effective in decreasing the load on the VLR/HLR but still hasthe other disadvantages.

A third proposed plan stores an ID of a source BSC initially accessed bythe mobile for a packet data service until the call is released, andperforms location management and dormant state management of thecorresponding mobile by utilizing the stored information. That is, whenthe mobile is activated in the dormant state, the mobile provides the IDof the initially accessed BSC (source BSC) to a newly accessed BSC(hereinafter, referred to a “target BSC”). In this case, when processinga registration message of the mobile, the target BSC can rapidly accessa dormant state database (DB) of the mobile whose packet service isactivated. However, to this end, the radio interface standard must bechanged undesirably. That is, the message format must be changed suchthat the mobile can transmit the ID of the source BSC to the target BSC.

A fourth proposed plan is to construct a small-scale VLR not unlike theVLR/HLR connected to a mobile switching center (MSC), and arrange thesmall-scale VLR in a network where a new server exclusively manages thedormant state of the mobiles. This small-scale VLR is constructed as aBSC. That is, the small-scale VLR is arranged in a network where aseparate server is constructed as a BSC, and the BSCs acquire and updatethe information on the data service call in the dormant state from theseparate server. In this case though, it is necessary to constructseparate hardware, and guarantee the VLR/HLR-level safety to the newdevice. In addition, from a viewpoint of the BSCs , there exists anoverhead that the BSCs should simultaneously register all theregistration messages in the MSC and the separate server as well.

SUMMARY OF THE INVENTION

It is, therefore, an object of the present invention to provide anapparatus and method for effectively embodying a packet data servicewithout a separate device and modification of the radio interfacestandard in a wireless packet data system.

It is another object of the present invention to provide an apparatusand method for managing mobiles in a dormant state in a BSC, therebyenabling termination of a packet call to the mobile and rapidreconnection.

It is further another object of the present invention to provide anapparatus and method for enabling reconnection to a previous PPP(Point-to-Point Protocol) access point in a BSC, upon receipt of a calloriginated from a mobile in a dormant state.

It is yet another object of the present invention to provide anapparatus and method for readily performing a service for managing amobile in a dormant state even though traffic through an IP (InternetProtocol) network becomes larger than a capacity of a voice call.

It is still another object of the present invention to provide anapparatus and method in which an error occurred in a certain BSC doesnot affect a service performed by another BSC.

It is still another object of the present invention to provide anapparatus and method in which BSCs have search and addition/deletionfunctions for effective database management by maintaining informationon the maximum number of mobiles in the dormant state.

According to one aspect of the present invention, there is provided amethod for storing dormant state information of mobile stations in adormant state where no packet data is exchanged with an external packetnetwork, in a centralized database connected to a packet data switch,and updating the dormant state information stored in the centralizeddatabase in association with the mobile stations when a mobile stationin the dormant state moves to a, target BSC adjacent to a source BSC ina wireless packet data system including a packet data switch node (PDSN)for connecting the external packet network to the mobile stationsthrough the packet data switch and the source BSC connected to thepacket data switch. The method comprises the steps of transmitting alocation registration message from the mobile station to the target BSCwhen the mobile station moves to the target BSC adjacent to the sourceBSC; upon receipt of the location registration message, transmitting alocation update message for updating a location of the mobile station,from the target BSC to the centralized database; upon receipt of thelocation update message, updating dormant state information for themobile station by the centralized database so as to connect the targetBSC to the source BSC; and transmitting a location update result messageindicating complete update of the dormant state information from thecentralized database to the target BSC.

Preferably, the dormant state information includes an identifier of themobile station, location information of the mobile station, a lastregistration time of the mobile station, and a source BSC ID of themobile station.

Further, the dormant state information includes identifiers forconnections used to exchange packet data of the mobile station in thedormant state, a temporary identifier temporarily assigned to the mobilestation, a service option and service configuration.

Preferably, the location update message includes an identifier of themobile station, and location information of the mobile station.

Preferably, the location information of the mobile station is anidentifier of the target BSC.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the presentinvention will become more apparent from the following detaileddescription when taken in conjunction with the accompanying drawings inwhich:

FIG. 1 is a diagram illustrating the state transitions in a mobilecommunication system according to an embodiment of the presentinvention;

FIG. 2 is a diagram illustrating a structure of a network having aseparate entralized database according to an embodiment of the presentinvention;

FIG. 3A is a diagram illustrating a structure of a network in which theentralized database is unified in a VLR according to an embodiment ofthe resent invention;

FIG. 3B is a diagram illustrating a structure of a network having theentralized database as an internal module of a specific BSC according toan embodiment of the present invention;

FIG. 4 is a diagram illustrating a structure of the centralized databaseaccording to an embodiment of the present invention;

FIG. 5 is a diagram illustrating configuration of dormant informationstored in a dormant state database according to an embodiment of thepresent invention;

FIG. 6 is a diagram illustrating a structure of a centralized databaseagent module according to an embodiment of the present invention;

FIG. 7 is a diagram illustrating configuration of information stored ina database of a source BSC according to an embodiment of the presentinvention;

FIG. 8 is a diagram illustrating a procedure for exchanging messagesduring initial packet call setup in the case where the source BSC isfixed, according to an embodiment of the present invention;

FIG. 9 is a diagram illustrating a procedure for exchanging messages toupdate mobility management information of a packet terminal in the casewhere he source BSC is fixed, according to an embodiment of the presentinvention;

FIG. 10 is a diagram illustrating a procedure for exchanging messagesdue to an origination call from the packet terminal in the case wherethe source BSC is fixed, according to an embodiment of the presentinvention;

FIG. 11 is a diagram illustrating a procedure for exchanging messagesdue to a termination call to the packet terminal in the case where thesource BSC is fixed, according to an embodiment of the presentinvention;

FIG. 12 is a diagram illustrating a procedure for exchanging messagesduring initial packet call setup in the case where the source BSC isdynamic, according to another embodiment of the present invention;

FIG. 13 is a diagram illustrating a procedure for exchanging messages toupdate mobility management information of a packet terminal in the casewhere the source BSC is dynamic, according to another embodiment of thepresent invention;

FIG. 14 is a diagram illustrating a procedure for exchanging messagesdue to an origination call from the packet terminal in the case wherethe source BSC is dynamic, according to another embodiment of thepresent invention; and

FIG. 15 is a diagram illustrating a procedure for exchanging messagesdue to a termination call to the packet terminal in the case where thesource BSC is dynamic, according to another embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A preferred embodiment of the present invention will be described hereinbelow with reference to the accompanying drawings. In the followingdescription, well-known functions or constructions are not described indetail since they would obscure the invention in unnecessary detail. Inaddition, the present invention can be applied to any wireless packetdata system supporting the high-speed packet data service having the“packet activation” and “packet deactivation” attributes such as anIS-95B system, as well as the future mobile communication system such asthe CDMA-200 system and the W-CDMA system.

Herein, the invention will be described with reference to a CDMA-2000system operating under the TIA (Telecommunication Industry Association)standard, and the “mobile communication system” refers to a CDMA system.

A channel structure of the CDMA-2000 system to which the presentinvention is applied is divided into logical channels and physicalchannels. In this case, the major logical channels and the majorphysical channels used by a MAC (Medium Access Control) channel of theCDMA-2000 system are defined as follows. For convenience, a prefix “r-”will be attached to reverse channels, while a prefix “f-” will beattached to forward channels.

First, a function of the logical channels will be described in detail.

A dedicated signaling channel (dsch) is exclusively assigned to aspecific mobile only in the active state or the control hold state. Inaddition, the dsch is used for transmitting and receiving anL3/Call-Control control message.

A dedicated MAC channel (dmch) is also exclusively assigned to aspecific mobile only in the active state or the control hold state. Inaddition, the dmch is used for transmitting and receiving a controlmessage of a MAC layer to control a dedicated traffic channel (dtch),and chiefly manages 5ms-messages.

A common MAC channel (cmch) is commonly assigned to a plurality ofmobiles only in the suspended state or the dormant state. In addition,the cmch is used for transmitting and receiving a control message of theMAC layer.

A dedicated traffic channel (dtch) is exclusively assigned to a specificmobile only in the active state, and used for transmitting and receivingthe traffic.

A common traffic channel (ctch) is commonly assigned to a plurality ofmobiles only in the dormant state, and used for transmitting andreceiving the traffic.

Next, a function of the physical channels will be described in detail.

A dedicated control channel (DCCH) is exclusively assigned to a specificmobile to control the mobile. In addition, the DCCH supports a DTX(Discontinuous Transmission) mode where the channel band is used onlywhen there exists the traffic to transmit. The respective users shareone code by using different orthogonal long codes.

A common control channel (CCCH) is acquired by a plurality of mobilesthrough competition, and is mapped with the logical channel cmch.

A fundamental channel (FCH) is a channel provided considering reversecompatibility with the IS-95 system, and can be utilized fortransmitting and receiving traffic control information like theconventional IS-95 fundamental channel.

A supplemental channel (SCH) is a channel corresponding to the IS-95Bsupplemental channel, and is based on an outband technique for chieflytransmitting the traffic. The SCH supports a scheme which is dynamicallyassigned or released by the logical dmch.

FIG. 1 illustrates state transitions of a MAC layer in a mobilecommunication system according to an embodiment of the presentinvention. Referring to FIG. 1, the MAC layer has a different stateaccording to a channel holding state, and each state transition takesplace through a timer or an artificial primitive. The respective statesshown in FIG. 1 will be described below.

A null state 110 is a pre-call setup state where there is no connectionand no information. An initialization state 112 is a state wherenegotiations are carried out at an initialization request of a packetservice, and in this state, call processing and various negotiations areperformed through a common channel. A control hold state 114 is a statewhere the dedicated control channels dsch/dmch are established after thechannel negotiation. In this case, the traffic channel is immediatelyassigned through the dmch. An active state 116 is a state where due toactivation of the traffic, the dedicated traffic channel dtch isassigned through the dmch, and then, the traffic is transmitted andreceived through the assigned channel. A suspended state 118 is a statewhere the dedicated channels dsch/dmch are released and various controlinformation is transmitted and received through the common channel. Adormant state 110 is a state where due to no traffic is exchanged for along time, every channel under the layer 2 is released and all theinformation is removed. In this state, only the PPP-related accessinformation is managed. Finally, a reconnect state 122 is a state towhich transition occurs if transmission traffic is generated in thedormant state 120, and in this state, the same procedure as the initialcall setup procedure is performed except the fact that the PPPinformation is maintained.

Meanwhile, the state transitions take place based on a timer, as shownin FIG. 1. That is, transition to the control hold state 114 happensonly when no traffic is exchanged for a set time T_active aftertransition to the active state 116 by acquiring the dedicated trafficchannel in the control hold state 114. When no traffic is exchanged fora set time T_hold in the control hold state 114, transition occurs tothe suspended state 118. If the non-traffic state (the state that notraffic is exchanged) is maintained until expiration of a set timeT_suspend in the suspended state 118, transition to the dormant state110 takes place. Although the state transition diagram of FIG. 1includes the suspended state 118, an embodiment of the invention canalso be applied to a system excluding the suspended state. In this case,if no traffic is generated for the set time T_active in the active state116, transition will happen directly to the dormant state 120 throughthe control hold state 114.

The invention manages a call of the mobile in the dormant state amongthe above states of the MAC layer, so as to rapidly transition to theactive state when it is necessary to resume transmitting the packet dataof the mobile. To this end, a structure of a centralized database(hereinafter, referred to as a “centralized DB”) and dormant informationmanaged by the centralized DB must be defined. In addition, a structureof a source BSC providing a packet service for the mobile in the dormantstate and a database managed by the source BSC must be also defined.

Structure of Centralized DB

As mentioned above, the present invention embodies the centralized DBfor managing the dormant information of the mobiles. It is possible toconsider the following two plans in embodying the centralized DB.

A first plan is to construct the centralized DB with a separate softwareor device. In this case, the corresponding network has a structure shownin FIG. 2. As illustrated in FIG. 2, the centralized DB, as a separatesoftware or device, is connected to a global access network (GAN) whichconnects the network elements to one another. The GAN shown in FIG. 2 isrepresented by a packet data switch for switching among a plurality ofBSCs, the centralized DB and a packet data switch node (PDP (Packet DataProcessor)).

In a second plan, in the existing mobile communication system chieflysupporting the voice call, a mobile merges the centralized DB into theVLR managing the location information, or develops or connects thecentralized DB to an internal module in a specific BSC. In this case,the corresponding network has the structures shown in FIGS. 3A and 3B.

Although the physical location of the centralized DB is different in theabove two plans, the centralized DB has the same operation. Therefore,the structure and operation of the embodiment will be described withreference to the first plan shown in FIG. 2.

The centralized DB must be so embodied to manage the dormant informationof the mobiles. Preferably, the centralized DB proposed as an example ofthe present invention has a structure shown in FIG. 4.

Referring to FIG. 4, a centralized DB 400 according to an embodiment ofthe present invention includes an interface processor 402, a transactionprocessor 404 and a dormant state database 406. The interface processor402 provides a communication-related input/output interface forexchanging information with the BSCs or MSC/VLR by the centralized DB400. The transaction processor 404 supports a function of, upon receiptof a query message from the BSC and MSC/VLR, searching the dormant statedatabase 406 for the corresponding information and then transmitting aresponse. In addition, the transaction processor 404 supports a functionof updating the information managed by the dormant state database 406based on the information from the BSCs and MSC/VLR. The dormant statedatabase 406 is an information storage for storing information on themobiles (or mobile stations (MSs)) existing in the dormant state.

Configuration of Dormant Information

Meanwhile, the dormant state database 406 included in the centralized DB400 must store the MS information (hereinafter, referred to as “dormantinformation”) required to implement the invention. The dormantinformation stored in the dormant state database 406 has theconfiguration shown in FIG. 5. The information shown in FIG. 5 can beclassified into mandatory information and optional information. Themandatory information is information required for a service of the MSwhich has entered the dormant state, while the optional information isinformation required for efficiently supporting the packet service ofthe MS by a wire network. Herein, the optional information is,information necessary for supporting rapid reconnection by omitting theadditional negotiation and authentication process when the MS in thedormant state transits to the active state.

First, as to the mandatory information shown in FIG. 5, IMSI(International Mobile Station Identifier) indicates an identifier foridentifying the MS, and Location Information indicates information onthe place where the MS having entered the dormant state is currentlylocated. Further, Last Registration Time indicates the last time whenthe MS has performed communication, and Source BSC ID indicates anidentifier of a BSC where a source packet data processor (PDP) of the MSexists. The PDP is a processor for managing a communication interfacebetween a PDSN (Packet Data Switch Node) and a BSC. The PDSN is anexternal packet network, and the Internet is a typical example of it.

Through the mandatory information, the invention identifies the MStransited from the dormant state to the active state depending on theIMSI and then detects the source BSC where there exists the connectionto the PDSN, used by the corresponding MS in the active state. Besides,when it is not necessary to manage the dormant information any longerbecause the MS has moved to another MSC area, the dormant informationassociated with the corresponding MS is deleted after a lapse of apredetermined time starting from the last registration time. Further,the invention traces the location of the MS in the dormant state for thetraffic received from the PDSN.

Next, as to the optional information shown in FIG. 5, Service Referenceindicates an identifier for the connections used by the MS whileperforming the packet data service, and TMSI (Temporary Mobile StationIdentifier) indicates an identifier temporarily assigned to the MS fromthe network. -Subscriber Profile means information on the MS or asubscriber using the radio packet service, Service Option meanscapability information indicating whether it is possible to support suchservices as voice, packet and facsimile services, and ServiceConfiguration means the configuration of information on channelstructure, data rate and quality of the service supported.

Structure of Source BSC

A structure of a centralized DB agent module of a source BSC accordingto an embodiment of the present invention is illustrated in FIG. 6. Asillustrated, the centralized DB agent module according to an embodimentof the present invention includes a mobility management module 610, acall control module 612, a radio resource management module 614, and aninterface module 620.

The mobility management module 610 performs a process related to themobility of the MS, the call control module 612 performs callsetup/release and call management for the voice or packet service of theMS, and the radio resource management module 614 supports management andassignment/release of the radio resources. The interface module 620, amodule for managing the dormant state of the MS to serve as a sourceBSC, includes an interface processor 622, an agent processor 624, and asource BSC database 626.

The interface processor 622 is a communication input/output module forenabling various modules in the BSC to communicate with the agentprocessor 624 performing the connection with the centralized DB 400. Theagent processor 624 transmits an information search request and aninformation update request received from the various modules in the BSCto the centralized DB, and then, processes the results. The source BSCdatabase 626 stores information necessary for serving as a source BSCfor the MS.

Structure of Source BSC Database

Meanwhile, the source BSC database managed by the source BSC to supportthe dormant state of the MS has a structure shown in FIG. 7. Referringto FIG. 7, IMSI (International Mobile Station Identifier) indicates anidentifier for identifying the MS, and ATM Connection ID indicates anidentifier for identifying ATM (Asynchronous Transfer Mode) connectionestablished between the source BSC and the PDSN while the MS performsthe packet service. Out-Of-Data Flag is a flag for indicating that thecorresponding information will be deleted after a lapse of predeterminedtime, if the MS having entered the dormant state fails to enter theactive state for a long time.

Among the above fields, the ATM Connection ID field indicates a channelidentifier used when the source BSC is connected to the PDSN in the ATMmode. Otherwise, when the source BSC is connected to the PDSN in anothercommunication mode, a different channel identifier for the correspondingcommunication mode is used.

Besides, like the centralized DB, the source BSC database has theoptional information required for enabling the wire network toeffectively support a packet service of the MS. Here, the optionalinformation is information necessary for supporting rapid reconnectionby omitting the additional negotiation and authentication process whenthe MS in the dormant state transits to the active state. Referring toFIG. 7, Subscriber Profile means information on the MS or a subscriberusing the radio packet service, Service Option means capabilityinformation indicating whether it is possible to support such servicesas voice, packet and facsimile services, and Service Configuration meansthe configuration of information on channel structure, data rate andquality of the service supported.

Meanwhile, the present invention proposes following two approaches basedon the above structures, in order to effectively manage the MSs in thedormant state.

A first approach is a “fixed source BSC plan”, in which once the MSinitiates the call, the source BSC continuously serves as a source untilthe corresponding MS releases the packet service. Such an approach isrelatively easy to embody. That is, since the traffic and the signalpath are simply extended according to movement of the MS, this approachcan be simply embodied. Therefore, it is possible to effectively supportthe packet service of the MS in the initial stage of the packet service.Message exchange scenarios required for embodying the first proposedplan are illustrated in FIGS. 8 to 11.

A second approach is a “dynamic source BSC plan”, unlike the firstapproach where the source BSC is not changed until the packet service ofthe MS is released. The dynamic source BSC plan is to move the sourceBSC for the MS to the BSC of a cell to which the MS belongs, as the MSmoves. That is, the second approach is proposed to resolve the problemthat occurs when a traffic path passes through a plurality of BSCs, asthe MS moves. Message exchange scenarios required for embodying thesecond proposed plan are illustrated in FIGS. 12 to 14.

Now, a detailed description of the two proposed plans will be made withreference to the above structures. There have been proposed threedifferent plan-based networks for the centralized DB according to anembodiment of the present invention. Herein, however, the description ofthe invention will be made with reference to the network based on theplan in which the centralized DB is constructed as a separate module, asset forth in FIG. 2. This is because the operation is performed in asimilar manner although the invention is applied to any of the threeproposed plans.

A message processing operation based on the “fixed source BSC plan”according to an embodiment of the present invention will be describedwith reference to the message exchange scenarios shown in FIGS. 8 to 11.

First, a message exchange scenario performed during initial packet callsetup in the case where the source BSC is fixed will be described withreference to FIG. 8. Referring to FIG. 8, in Step #1, the MS transmitsan origination message to the BSC to attempt a PPP (Point-to-PointProtocol) access for the purpose of a packet service. Here, the BSCbecomes a source BSC. The transmitted origination message is received atthe BSC serving a cell in which the MS is located. In Step #2, uponreceipt of the origination message, the BSC transmits to the centralizedDB 400 a query message Serv_Query_MSG followed by an acknowledgementfrom the MS. The query message Serv_Query_MSG includes IMSI informationdesignating the MS that has transmitted the origination message.

The centralized DB 400 processes the Serv_Query_MSG transmitted from theBSC. More specifically, the interface processor 402 in the centralizedDB 400 receives the Serv_Query_MSG, and provides it to the transactionprocessor 404. The transaction processor 404 then searches the dormantinformation stored in the dormant state DB 406, and determines whetherthere exists the dormant information corresponding to theServ_Query_MSG. Determining whether there exists the dormant informationis performed by determining whether there exists dormant informationcorresponding to the IMSI included in the Serv_Query_MSG. The dormantinformation, as described with reference to FIG. 5, is informationrequired for the rapid reconnection or for tracking the location of thedormant state MS.

If the Serv_Query_MSG provided by the origination message from the MS isfor the transition from the dormant state to the active state, thecorresponding dormant information is stored in the dormant state DB 406.If the MS requests the packet service for the first time, or that the MSrequest the packet service for the first time after moving from anotherMSC the corresponding dormant information is not stored in the dormantstate DB 406. If it is determined through the search that the dormantinformation of the corresponding MS is not stored, the transactionprocessor 404 transmits to the BSC a response message Serv_Result_MSGindicating that there is no dormant information for the MS, in Step #3.However, if it is determined that the dormant information of thecorresponding MS is stored, an operation of FIG. 10 is performed, whichwill be described later.

Upon receipt of the Serv_Result_MSG from the centralized DB 400, the BSCdetermines whether the origination message received from the MS is anorigination message caused by a new call or a call incoming from anotherMSC. Determining whether to designate the BSC as a source BSC for thecorresponding MS is performed based on whether the origination messageis an origination message caused by a new call or a call incoming fromanother MSC. If it is determined from the Serv_Result_MSG that theorigination message from the MS is an origination message caused by anew call or a call incoming from another MSC, the BSC assigns aninternal traffic processor (ATP) according to a load balancing rule. TheATP is a processor for controlling the overall operation for providingthe packet service to the MS. In addition to the assignment of the ATP,the source BSC sets as a new call the information caused by the callattempted by the MS through the MSC/VLR, and then separately managesinformation on the set new call. In order to configure the informationon the new call, it is necessary to determine PPP address and PPP ID ofthe PDP (PDSN).

The operation of registering a new call through the MSC/VLR is anoperation commonly performed to provide an initial packet service, sothe detailed description will be omitted. When the new call setupprocess is completed, the MS performs the packet communication servicethrough the source BSC according to the standard.

During the packet communication service, the source BSC monitors whetherthe MS transits to the suspended state or the dormant state. Asmentioned above, the transition to the suspended state or the dormantstate takes place when no data is exchanged for a predetermined time.Upon detecting the MS's transition to the suspended state or the dormantstate, the source BSC proceeds to Step #4-1. In Step #4-1, the sourceBSC releases the currently assigned connection (channel) by transmittinga release message to the MS. Further, in Step #4-2, the source BSCtransmits to the centralized DB 400 a Serv_Update_MSG message forrequesting update of the dormant information corresponding to the MStransited to the suspended state or the dormant state. Here, theServ_Update_MSG includes the dormant information of the correspondingMS. The dormant information is information necessary for the resumptionof the packet service to the MS transited to the suspended state or thedormant state, and its exemplary structure is shown in FIG. 5.

Upon receipt of the Serv_Update_MSG, the centralized DB 400 creates anew DB field into its internal dormant state DB 406, and stores thedormant information included in the Serv_Update_MSG in the createdfield. After completion of storing the dormant information, thecentralized DB 400 proceeds to Step #4-3 to transmit to the source BSC aServ_Update_Ack_MSG message indicating that update of the dormantinformation has been normally completed, thus completing the initialpacket call setup process.

Although a detailed description has not been made regarding a commonoperation in which the state transition does not happen and the packetservice is normally ended after the MS sets up the initial packet call,the operation will be performed in the same process as the conventionalprocess.

The above embodiment has disclosed a scheme for updating the dormantinformation of the MS in the centralized DB 400 at the point in timewhere the MS transits from the active state to the suspended state orthe dormant state after completion of the initial packet call setup.However, an alternative embodiment creates a new DB field prior toperforming the packet service when there exists no information on thecorresponding call in the centralized DB 400, and then updates thedormant information of the MS for the call. In this case, it isnecessary to define a field for the dormant information to be updated inthe Serv_Query_MSG transmitted in Step #2 of FIG. 8, and the procedureperformed in Steps #4-2 and #4-3 of FIG. 8 must be included in theprocedure performed in Steps #2 and #3 of FIG. 8.

Second, in a message exchange scenario for update of the mobilitymanagement information of a packet terminal in the case where the sourceBSC is fixed, a target BSC updates location information of the dormantinformation of managed in the centralized DB upon receipt of aregistration message due to an idle handoff of the dormant state MS.This will be described in detail with reference to FIG. 9.

Referring to FIG. 9, in Step #1, the MS in the dormant state transmits aregistration message due to an idle handoff, and the locationregistration message transmitted by the MS is received at a target BSC.The “target BSC” refers to a BSC to which the moving MS desires to beregistered. Upon receipt of the location registration message in Step#1, the target BSC transmits, though not illustrated, a locationupdating request message to the MSC to update the location informationmanaged in the VLR.

In Step #2, the target BSC transmits a location update msgLoc_Query_Update_MSG to the centralized DB 400 to determine whether apacket service of the MS from which the registration message has beenreceived is activated and updates the location information. TheLoc_Query_Update_MSG must include the IMSI for identifying thecorresponding MS. The location information, as stated above, isinformation on the place where the MS is currently located. For example,a BSC identifier for identifying the target BSC can be used for thelocation information. Upon receipt of the Loc_Query_Update_MSG, thecentralized DB 400 determines whether there exists the dormantinformation for the corresponding MS using the IMSI constituting theLoc_Query_Update_MSG. If it is determined that the dormant informationof the MS exists, the centralized DB 400 determines that thecorresponding MS is a dormant state MS whose packet service isactivated, using a location update result message Loc_Result_MSGtransmitted to the target BSC in Step #3. In addition, the centralizedDB 400 updates the location information for the MS based on the locationinformation (identifier of the target BSC) constituting theLoc_Query_Update_MSG. Upon receipt of the location result messageLoc_Result_MSG indicating activation of the packet service, the targetBSC regards the packet service state of the corresponding MS as thedormant state or the null state. The reason is because the dormantinformation managed in the centralized DB 400 proves that thecorresponding MS is in the dormant state or the null state. However,upon failure to find the dormant information for the corresponding MS,the centralized DB 400 informs that the packet service of the MS is notactivated, using the location result message Loc_Result_MSG transmittedto the target BSC in Step #3.

Third, in a message exchange scenario caused by an origination call froma packet terminal in the case where the source BSC is fixed, a targetBSC is provided with the dormant information for the corresponding MSfrom the centralized DB 400 upon receipt of an origination message fromthe MS in the dormant state, and provides a packet service to thecorresponding MS using the provided dormant information. This will bedescribed in detail with reference to FIG. 10.

In order to resume the packet service, the MS in the dormant statetransmits an origination message to the BSC. That the MS in the dormantstate has transmitted an origination message is equivalent to requestingtransition to the active state. Referring to FIG. 10, in Step #1, thetransmitted origination message is provided to a BSC where the MS iscurrently located. Here, the BSC provided with the origination messagebecomes a target BSC of the MS. In Step #2, the target BSC transmits tothe centralized DB 400 a dormant information request messageServ_Query_MSG for requesting dormant information of the MS. TheServ_Query_MSG must include IMSI for selecting dormant information forthe MS out of the information stored in the centralized DB 400 and atarget BSC ID for providing the selected dormant information.

Upon receipt of the Serv_Query_MSG, the centralized DB 400 searches thedormant information of the corresponding MS based on the IMSI includedin the Serv_Query_MSG. Searching the dormant information is performed bycomparing the IMSIs stored in the centralized DB 400 with the IMSIprovided from the target BSC and determining whether there exists thesame IMSI. After completing the dormant search, the centralized DB 400transmits the search results to the target BSC through a search resultmessage Serv_Result_MSG in Step #3 of FIG. 10. The Serv_Result_MSG hasdormant information including the source BSC ID. Upon receipt of thedormant information of the corresponding MS through the Serv_Result_MSG,the target BSC attempts packet call connection to the source BSC in Step#4. If the packet call connection is set up, the packet call to the MSis reconnected by connecting the internal PDP to the network through thesource BSC. This means the transition from the dormant state to theactive state.

Therefore, by managing the dormant information for the MS in the dormantstate in the centralized DB 400 accessible by every BSC in the same MSC,it is possible to rapidly perform the packet service when the transitionto the active state occurs due to the call origination by the MS.

Fourth, in a message exchange scenario caused by a termination call to apacket terminal in the case where the source BSC is fixed, if atermination call to the dormant state MS located in a target BSC isgenerated from the MSC, a source BSC informs the target BSC of theterminal call by consulting the centralized DB 400, and the target BSCprovides the information to the corresponding MS, thus provides a packetservice to the MS by receiving a response message. This will bedescribed in detail with reference to FIG. 11.

Referring to FIG. 11, in Step #1, the source BSC receives a packetarrival event upon receipt of a termination call requesting terminationto a certain MS from a given PDP through an interface link (acommunication link between the source BSC and the PDSN). In Step #2, thesource BSC transmits to the centralized DB 400 a query messageLoc_Query_MSG (MISI) for determining a location of the corresponding MSin response to the termination call. The query message Loc_Query_MSGincludes IMSI information for identifying the MS. The centralized DB 400searches the location information of the corresponding MS based on theIMSI. After the search, the centralized DB 400 transmits the searchedlocation information of the MS to the source BSC through a locationinformation message Loc_Result_MSG (Loc Info) in Step #3. Upon receiptof the location information of the MS, the source BSC analyzes thelocation of the corresponding MS based on the received locationinformation. After analyzing the location of the MS, the source BSCtransmits a paging request message to the target BSC where the MS islocated, in Step #4. Though not illustrated in the drawing, upon failureto receive a response message Paging_Response_Ack_MSG in response to thepaging request message for a predetermined time, the source BSC performsan operation according to a paging algorithm.

Upon receipt of the paging request message, the target BSC transmits apage message Page_MSG to every MS in its cell area through abroadcasting channel in Step #5. Upon receipt of the page messagetransmitted through the broadcasting channel, the MS transmits a pageresponse message to the target BSC in response to the page message inStep #6. Upon receipt of the page response message, the target BSCtransmits a paging response acknowledge message to the source BSC inorder to set up a packet call in Step #7. Upon receipt of the pagingresponse acknowledge message from the target BSC, the source BSCtransmits a packet call connection message for call connection to thetarget BSC in Step #8. Upon receipt of the packet call connectionmessage, the target BSC performs an operation for the packet service.

A packet reception path to the MS for the packet service is connected inthe sequence of PDP (PDSN)→source BSC→target BSC→MS as represented by abold solid line. On the other hand, a transmission path from the MS forthe packet service has a reverse direction of the reception path.

To sum up, in the first plan, if the MS initially sets up a call atBSC#l and then moves to BSC#2, BSC#3 and BSC#4, a traffic path for thepacket service caused by a termination call is set in the sequence ofPDSN→source BSC#1→BSC#2→BSC#3→BSC#4→MS, while a traffic path for thepacket service caused by an origination call is set in the sequence ofMS→BSC#4→BSC#3→BSC#2→source BSC#1→PDSN.

Next, a message processing operation based on the “dynamic source BSCplan” according to another embodiment of the present invention will bedescribed with reference to the message exchange scenarios shown inFIGS. 12 to 15.

First, a message exchange scenario performed during initial, packet callsetup in the case where the source BSC is dynamically changed accordingto movement of the MS will be described with reference to FIG. 12.Referring to FIG. 12, in Step #1, the MS transmits an originationmessage to the BSC to attempt a PPP (Point-to-Point Protocol) access forthe purpose of a packet service. The transmitted origination message isreceived at the BSC serving a cell to which the MS belongs. In Step #2,upon receipt of the origination message, the BSC transmits to thecentralized DB 400 a query message Serv_Query_MSG followed by anacknowledgement from the MS. The query message Serv_Query_MSG includesinformation (MS identifier, hereinafter referred to as IMSI) designatingthe MS that has transmitted the origination message.

The centralized DB 400 processes the Serv_Query_MSG transmitted from theBSC. More specifically, the interface processor 402 in the centralizedDB 400 receives the Serv_Query_MSG, and provides it to the transactionprocessor 404. The transaction processor 404 then searches the dormantinformation stored in the dormant state DB 406, and determines whetherthere exists the dormant information corresponding to theServ_Query_MSG. Determining whether there exists the dormant informationis performed by determining whether there exists dormant informationcorresponding to the IMSI included in the Serv_Query_MSG. The dormantinformation, as described with reference to FIG. 5, is informationrequired for the rapid reconnection or for tracking the location of thedormant state MS.

If the Serv_Query_MSG provided by the origination message from the MS isfor the transition from the dormant state to the active state, thecorresponding dormant information is stored in the dormant state DB 406.If the MS requests the packet service for the first time, or that the MSrequest the packet service for the first time after moving from anotherMSC, the corresponding dormant information is not stored in the dormantstate DB 406. If it is determined through the search that the dormantinformation of the corresponding MS is not stored, the transactionprocessor 404 transmits to the BSC a response message Serv_Result_MSGindicating that there is no dormant information for the MS, in Step #3.However, if it is determined that the dormant information of thecorresponding MS is stored, an operation of FIG. 15 is performed, whichwill be described later.

Upon receipt of the Serv_Result_MSG from the centralized DB 400, the BSCdetermines whether the origination message received from the MS is anorigination message caused by a new call or a call incoming from anotherMSC. Determining whether to designate the BSC as a source BSC for thecorresponding MS is performed based on whether the origination messageis an origination message caused by a new call or a call incoming fromanother MSC. If it is determined from the Serv_Result_MSG that theorigination message from the MS is an origination message caused by anew call or a call incoming from another MSC, the BSC assigns aninternal traffic processor (ATP) according to a load balancing rule. TheATP is a processor for controlling the overall operation for providingthe packet service to the MS. In addition to assignment of the ATP, thesource BSC sets as a new call the information caused by the callattempted by the MS through the MSC/VLR, and then separately managesinformation on the set new call. In order to configure the informationon the new call, it is necessary to determine PPP address and PPP ID ofthe PDP (PDSN).

The operation of registering a new call through the MSC-VLR is anoperation commonly performed to provide an initial packet service, sothe detailed description will be omitted. When the new call setupprocess is completed, the MS performs the packet communication servicethrough the source BSC according to the standard.

During the packet communication service, the source BSC monitors whetherthe MS transits to the suspended state or the dormant state. Asmentioned above, the transition to the suspended state or the dormantstate takes place when no data is exchanged for a predetermined time.Upon detecting the MS's transition to the suspended state or the dormantstate, the source BSC proceeds to Step #4-1. In Step #4-1, the sourceBSC releases the currently assigned connection (channel) by transmittinga release message to the MS. Further, in Step #4-2, the source BSCtransmits to the centralized DB 400 a Serv_Update_MSG message forrequesting update of the dormant information corresponding to the MStransited to the suspended state or the dormant state. Here, theServ_Update_MSG must include the dormant information of thecorresponding MS. The dormant information means information necessaryfor resumption of the packet service to the MS transited to thesuspended state or the dormant state, and its exemplary structure isshown in FIG. 5.

Upon receipt of the Serv_Update_MSG, the centralized DB 400 creates anew DB field into its internal dormant state DB 406, and stores thedormant information included in the Serv_Update_MSG in the createdfield. After completion of storing the dormant information, thecentralized DB 400 proceeds to Step #4-3 to transmit to the source BSC aServ_Update_Ack_MSG message indicating that update of the dormantinformation has been normally completed, thus completing the initialpacket call setup process.

Although a detailed description has not been made regarding a commonoperation in which the state transition does not happen and the packetservice is normally ended after the MS sets up the initial packet call,the operation will be performed in the same process as the conventionalprocess.

The above embodiment has disclosed a scheme for updating the dormantinformation of the MS in the centralized DB 400 at the point in timewhere the MS transits from the active state to the suspended state orthe dormant state after completion of the initial packet call setup.However, an alternative embodiment creates a new DB field prior toperforming the packet service when there exists no information on thecorresponding call in the centralized DB 400, and then updates thedormant information of the MS for the call. In this case, it isnecessary to define a field for recording the dormant information to beupdated in the Serv_Query_MSG transmitted in Step #2 of FIG. 12, and theprocedure performed in Steps #4-2 and #4-3 of FIG. 12 must be includedin the procedure performed in Steps #2 and #3 of FIG. 12.

Second, a message exchange scenario for update of the mobilitymanagement information of a packet terminal in the case where the sourceBSC is dynamically changed according to movement of the MS, will bedescribed in detail with reference to FIG. 13.

Referring to FIG. 13, in Step #1, the MS in the dormant state transmitsa registration message due to an idle handoff, and the locationregistration message transmitted by the MS is received at a target BSC.The “target BSC” refers to a BSC to which the moving MS desires to beregistered. That is, the target BSC includes all the BSCs other than thesource BSC of the corresponding MS, among the BSCs constituting the sameMSC. Upon receipt of the location registration message in Step #1, thetarget BSC transmits, though not illustrated, a location updatingrequest message to the MSC to update the location information managed inthe VLR.

In Step #2, the target BSC transmits a location update messageLoc_Query_Update_MSG to centralized DB 400 to determine whether a packetservice of the MS from which the registration message has been receivedis activated and updates the location information. TheLoc_Query_Update_MSG must include the IMSI for identifying thecorresponding MS. The location information, as stated above, isinformation on the place where the MS is currently located. For example,a BSC identifier for identifying the target BSC can be used for thelocation information. Upon receipt of the Loc_Query_Update_MSG, thecentralized DB 400 transmits in Step #3 to a PDP a location informationupdate request message Loc_Update_Source_MSG for requesting that thesource BSC corresponding to the MS that has transmitted the registrationmessage should be changed to a target BSC. Upon receipt of the locationinformation update request message Loc_Update_Source_MSG, the PDPtransmits an acknowledge message Loc_Update_Ack_MSG to the centralizedDB 400 after designating the target BSC as a new source BSC.

Upon receipt of the acknowledge message Loc_Update_Ack_MSG, thecentralized DB 400 searches for the MS in the dormant information usingthe IMSI in the Loc_Query_Update_MSG. After finding the dormantinformation for the MS, the centralized DB 400 informs that thecorresponding MS is a dormant state MS whose packet service isactivated, using a location result message Loc_Result_MSG transmitted tothe updated source BSC in Step #5. In addition, the centralized DB 400updates the location information for the MS based on the locationinformation (identifier of the target BSC) constituting theLoc_Query_Update_MSG. Upon receipt of the location result messageLoc_Result_MSG indicating activation of the packet service, the updatedsource BSC regards the packet service state of the corresponding MS asthe dormant state or the null state. The fact that the dormantinformation is managed in the centralized DB 400 proves that thecorresponding MS is in the dormant state or the null state. However,upon failure to find the dormant information for the corresponding MS,the centralized DB 400 informs that the packet service of the MS is notactivated, using the location result message Loc_Result_MSG transmittedto the updated source BSC in Step #5.

Third, a message exchange scenario caused by an origination call from apacket terminal in the case of the source BSC is dynamically changedaccording to movement of the MS will be described in detail withreference to FIG. 14.

In order to resume the packet service, the MS in the dormant statetransmits an origination message to the BSC. The fact that the MS in thedormant state has transmitted an origination message is equivalent torequesting transition to the active state. Referring to FIG. 14, in Step#1, the transmitted origination message is provided to a BSC where theMS is currently located. Here, the BSC provided with the originationmessage becomes a target BSC of the MS. In Step #2, the target BSCtransmits to the centralized DB 400 a dormant information requestmessage Serv_Query_MSG for requesting dormant information of the MS. TheServ_Query_MSG must include the IMSI for selecting dormant informationfor the MS out of the information stored in the centralized DB 400 and atarget BSC ID for providing the selected dormant information.

Upon receipt of the Serv_Query_MSG, the centralized DB 400 searches thedormant information of the corresponding MS based on the IMSI includedin the Serv_Query_MSG. Searching the dormant information is performed bycomparing the IMSIs stored in the centralized DB 400 with the IMSIprovided from the target BSC and determining whether there exists thesame IMSI. After completing the dormant search, the centralized DB 400transmits the search results to the target BSC through a search resultmessage Serv_Result_MSG in Step #3 of FIG. 14. The Serv_Result_MSG hasdormant information including the source BSC ID. Upon receipt of thedormant information of the corresponding MS through the Serv_Result_MSG,the target BSC connects a packet call to the MS by connecting theinternal PDP to the network based on the provided dormant information inStep #4 of FIG. 14.

Therefore, by managing the dormant information for the MS in the dormantstate in the centralized DB 400 accessible by every BSC in the same MSC,it is possible to rapidly perform the packet service when the transitionto the active state occurs due to the call origination by the MS.

As described above, when the source BSC is dynamically changed accordingto movement of the MS, the target BSC is designated as a new source BSCin the centralized DB 400, so that the packet service is performedwithout passing through the existing source BSC. That is, the target BSC(the updated source BSC) performs the packet service directly with thePDP (PDSN).

Fourth, a message exchange scenario caused by a termination call to apacket terminal in the case where the source BSC is dynamically changedaccording to movement of the MS will be described in detail withreference to FIG. 15.

Referring to FIG. 15, in Step #1, the PDSN transmits a setup message toa target BSC upon receipt of a data packet from a certain PDP. In Step#2, the target BSC transmits to the centralized DB 400 a query messageLoc_Query_MSG for determining a location of the corresponding MS inresponse to the setup message. The query message Loc_Query_MSG includesIMSI information for identifying the MS. The centralized DB 400 searchesthe location information of the corresponding MS based on the IMSI.After completion of the search, the centralized DB 400 transmits thesearched location information of the MS to the target BSC through amessage Loc_Result_MSG in Step #3. Upon receipt of the locationinformation of the MS, the target BSC analyzes the location of thecorresponding MS based on the received location information. Afteranalyzing the location of the MS, the target BSC transmits a pagingrequest message to itself in Step #4. Though not illustrated in thedrawing, upon failure to receive a paging request acknowledge messagefor a predetermined time, the target BSC performs a paging algorithm.

Upon receipt of the paging request message, the target BSC transmits apage message Page_MSG to every MS in its cell area through abroadcasting channel in Step #5. Upon receipt of the page messagetransmitted through the broadcasting channel, the MS transmits a pageresponse message to the target BSC in response to the page message inStep #6. Upon receipt of the page response message, the target BSCtransmits a paging response acknowledge message to itself in order toset up a packet call in Step #7.

In Step #8, the target BSC transmits to the centralized DB 400 a querymessage Serv_Query_MSG for requesting service information of the MS.Then, in Step #9, the centralized DB 400 searches the serviceinformation of the MS and transmits to the target BSC a Serv_Result_MSGmessage indicating the searched service information. The Serv_Result_MSGincludes PPP information for the MS. The target BSC transmits a packetcall connection request to the PDSN based on the received information.

A packet reception path to the MS for the packet service according tothe second embodiment is connected in the sequence of PDP (PDSN)→targetBSC →MS as represented by a bold solid line. On the other hand, atransmission path from the MS for the packet service has a reversedirection of the reception path.

As described above, since the PPP information of the packet servicecalls entered in the dormant state is managed in the centralized DB, thepresent invention has the following advantages:

(1) The IS-95B or CDMA-2000 mobile communication system can manage thelocation of a packet call in the dormant state without modification ofBSC/HLR/VLR and MS.

(2) The BSC can perform by itself call terminal and call origination ona packet terminal in the dormant state.

(3) The MS in the dormant state can make a reconnection to a previousPPP access point in case of call origination.

(4) It is possible to provide a rapid reconnection function when the MSin the dormant state is activated for packet transmission.

(5) It is possible to support simple structure, which can be embodiedwith the additional module of the existing devices such as VLR and BSC.

(6) It is possible to minimize a load on the wire and wireless stages,since the registration and authentication process is not performed againduring reconnection of the packet call in the dormant state.

(7) When the centralized DB is embodied with a separate device, thelocation management processor such as MSC/VLR has reduced load, so thatit is possible to effectively manage the maximum number of subscribersin the MSC.

While the invention has been shown and described with reference to acertain preferred embodiment thereof, it will be understood by thoseskilled in the art that various changes in form and details may be madetherein without departing from the spirit and scope of the invention asdefined by the appended claims.

1. A method for reconnecting an exchange of packet data between a mobile station and an external packet network by storing dormant state information of mobile stations in a dormant state where no packet data is exchanged with the external packet network, in a centralized database connected to a packet data switch, and updating the dormant state information stored in the centralized database in association with the mobile station when the mobile station in the dormant state moves to a target BSC adjacent to a source BSC in a wireless packet data system including a packet data switch node (PDSN) for connecting the external packet network to the mobile stations through the packet data switch and the source BSC connected to the packet data switch, the method comprising the steps of: upon receipt of a termination call requesting termination of packet data from the external packet network, transmitting from the source BSC to the centralized database a query message for determining a location of the mobile station for the termination call; upon receipt of the query message, searching dormant state information stored in association with the mobile station in the centralized database and transmitting the searched dormant state information to the source BSC using a location information message; upon receipt of the location information message, transmitting from the source BSC to the target BSC where the mobile station is located a paging request message for requesting paging of the mobile station; upon receipt of the paging request message, paging by the target BSC the mobile station and transmitting a page response acknowledge message acknowledging the paging to the source BSC when the mobile station responds to the paging; upon receipt of the paging response acknowledge message, transmitting from the source BSC to the target BSC a packet call connection message requesting connection of the packet data, and thus connecting the source BSC to the target BSC through the packet data switch.
 2. The method as claimed in claim 1, wherein the dormant state information includes an identifier of the mobile station, location information of the mobile station, a last registration time of the mobile station, and a source BSC ID of the mobile station.
 3. The method as claimed in claim 2, wherein the dormant state information includes identifiers for connections used to exchange packet data of the mobile station in the dormant state, a temporary identifier assigned to the mobile station, a service option and service configuration.
 4. The method as claimed in claim 1, wherein the query message includes an identifier of the mobile station for the termination call.
 5. A method for reconnecting an exchange of packet data between a mobile station and an external packet network by storing dormant state information of mobile stations in a dormant state where no packet data is exchanged with the external packet network, in a centralized database connected to a packet data switch, and updating the dormant state information stored in the centralized database in association with the mobile station when the mobile station in the dormant state moves to a target BSC adjacent to a source BSC in a wireless packet data system including a packet data switch node (PDSN) for connecting the external packet network to the mobile stations through the packet data switch and the source BSC connected to the packet data switch, the method comprising the steps of: upon receipt of a termination call requesting termination of packet data from the external packet network through the PDSN, transmitting from the target BSC to the centralized database, a query message for determining a location of the mobile station for the termination call; upon receipt of the query message, analyzing by the centralized database dormant state information stored in association with the mobile station and transmitting the analyzed dormant state information to the target BSC using a location information message; upon receipt of the location information message, generating by the target BSC an internal paging request message and transmitting by the target BSC a page message for paging the mobile station based on the paging request message; upon receipt of a paging response message from the mobile station in response to the page message, generating an internal paging response acknowledge message and transmitting to the centralized database a query message for requesting service information of the mobile station; upon receipt of the query message, transmitting from the centralized database to the target BSC the service information stored in association with the mobile station using a given message; and upon receipt of the service information, transmitting from the target BSC to the PDSN a packet call connection message for requesting connection of the packet data and thus connecting the PDSN to the target BSC through the packet data switch.
 6. The method as claimed in claim 5, wherein the dormant state information includes an identifier of the mobile station, location information of the mobile station, a last registration time of the mobile station, and a source BSC ID of the mobile station.
 7. The method as claimed in claim 6, wherein the dormant state information includes identifiers for connections used to exchange packet data of the mobile station in the dormant state, a temporary identifier assigned to the mobile station, a service option and service configuration.
 8. The method as claimed in claim 5, wherein the query message includes an identifier of the mobile station for the termination call. 